Windows 2000 does not Shutdown

Hi,
I have a windows 2000 server installed, which works absolutely fine without giving any errors. The reboots after installtion were absolute normal. When i try shutting down the sys from start>shutdown or using cntl + alt + del or by using Alt + F4. It comes back to the desktop without shuttingdown …. basically it does not recognise the shutdown command.
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Rd,
Satyen.